Algae commonly infests and grows in bodies of water, particularly water exposed to the sun or other sources of light. The problem of algae growth affects swimming pools, spas, lakes, rivers, reservoirs, industrial water systems, and other bodies of water.
In swimming pools, algae growth is particularly a problem in the summer, when the water temperature is relatively high and the concentration of nutrients such as nitrate and phosphate in the water increases.
Chemicals have long been added to water to combat the algae problem. Such chemicals are referred to here as "algae control agents" if they either kill algae (i.e. are algicidal) or arrest the growth of algae (i.e. are algistatic) when an effective amount of the chemical in question is dispersed in a body of water.
There are several algae treatment compounds marketed. They include copper, silver, quaternary ammonium compounds, polymeric quaternary ammonium compounds, bromine and chlorine. Each of these types of products has its own strengths and weaknesses. Copper and silver kill algae fast, and at low levels, but they can cause staining of the surfaces as well as discoloration of the water if used incorrectly. Quaternary ammonium compounds kill algae and are inexpensive, but they cause foaming and their effectiveness is fairly short lived in a pool. Polymeric quaternary ammonium algicides do not foam or cause staining, but in order to kill algae, high levels must be added. Chlorine and bromine are both capable of killing algae, but the levels required are high and no one can use the pool until chemical levels are returned to normal.
Ionenes have been suggested for use as microbiocides for the microorganisms, including algae, which grow in industrial water systems. See, for example, U.S. Pat. No. 4,506,081, column 4, lines 15-35, and column 10, lines 16-68; U.S. Pat. No. 5,419,897, column 2, lines 5-20. Ionenes are polymeric quaternary ammonium compounds having the structures and properties and made by the processes specified in U.S. Pat. Nos. 4,506,081; 4,778,813; 4,581,058; and 5,419,897; which are incorporated here by reference in their entireties for their disclosure of ionenes.
Water-dispersible di-lower-alkyl ammonium halide polymers such as poly (dimethyl diallyl ammonium chloride) function as coagulants, and some of them (AGEFLOC WT-20 and W-40) have been identified by the manufacturer as being EPA approved for use as water clarifying agents in potable water and waste water.